class Solution {

    public boolean exist(char[][] board, String word) {

        for(int i=0; i<board.length; i++) {

            for(int j=0; j<board[0].length; j++) {

                if(exist(board, i, j, word, 0))

                    return true;

            }

        }

        return false;

    }

    public boolean exist(char[][] board, int x, int y, String word, int index) {

        if(index == word.length()) return true;

        if(x < 0 || y<0 || x>=board.length || y>=board[0].length || board[x][y] != word.charAt(index))

            return false;

        board[x][y] ^= 128;

        boolean exist = exist(board, x-1, y, word, index+1) ||

                        exist(board, x+1, y, word, index+1) ||

                        exist(board, x, y-1, word, index+1) ||

                        exist(board, x, y+1, word, index+1) ;

        board[x][y] ^= 128;

        return exist;

    }

}

 class Solution:

     def dfs(self,board,word,index,rows,coloums,visited,i,j):

         if index >= len(word):

             return True

         if i >= rows or i <  or j >= coloums or j <  or visited[i][j] ==  or board[i][j] != word[index]:

             return False

         visited[i][j] =

         result = self.dfs(board,word,index+,rows,coloums,visited,i+,j) or self.dfs(board,word,index+,rows,coloums,visited,i-,j) or self.dfs(board,word,index+,rows,coloums,visited,i,j+) or self.dfs(board,word,index+,rows,coloums,visited,i,j-)

         visited[i][j] = 

         return result

     def exist(self, board: 'List[List[str]]', word: 'str') -> 'bool':

         rows = len(board)

         coloums = len(board[])

         visited = [[ for a in range(coloums)] for b in range(rows)]

         for i in range(rows):

             for j in range(coloums):

                 if self.dfs(board,word,,rows,coloums,visited,i,j):

                     return True

         return False